Method and apparatus for compacting the placement material in road building

ABSTRACT

A machine applies a layer of paving material to a subgrade to form a road. Immediately in front of the transverse line along which the material is deposited, the subgrade is vibrated in a manner such that the vibrations extend rearwardly and under the paving material being deposited on the subgrade to compact and cohere that material and adhere it to the subgrade.

United States Patent 1 1 A [111 ,752,592

Paar et al. Aug. 14, 1973 METHOD AND APPARATUS FOR 2.893.299 7/1959 Moir 94/48 COMPACTING THE PLACEMENT. 2.951.254 10/1960 MATERIAL IN ROAD BUILDING .7 r 7 2,044,883 6/1936 [75] Inventors: Alois Paar, Dusseldorf; Fritz 2,633,781 4/1953 Kiinig, Wuppertal-Vohwinkel, both ,253,522 5/1966 of Germany .508.476 4/1970 2,150,325 3/1939 Jackson "I: ..94/4:; [73] Assignee: Losenllanse n Mzi scli innbnn AG,

Dusseldorf-Grafenberg, Germany Primary Examiner--Nile c. Byers, Jr.

' Attorney-Howard H. Darbq et a1. [22] Filed: Apr. 29, 1971 1 [21] Appl. No.: 105,821 [57] CT A machine applies a layer of paving material to a sub- [301 Ford Appuuflon Priomy grade m form a road. Immediately in from of the trans- I May 2, 1970 7 Germany P 20 21 457.7 vex-c line along which he material Mimi the A 1 aubgrade 1| vibrated in a manner such that the vibra [52] US. Cl. 404/102 extend egrwafdly and under the paving material [51] ll". CI. 1301c 7/26 being deposited on the subgrade tocompactland [58] Field of Search 94/46, 48, 39 here h material and adhere the subgrade.

[56] References Cited 6 Claims, 1 Drawing Figure UNITED STATES PATENTS 2,757,588 8/1956 Pollitz 94/48 METHOD AND APPARATUS FOR COMPACTING THE PLACEMENT MATERIAL IN ROAD BUILDING BACKGROUND AND SUMMARY OF THE INVENTION The invention relates to a method and apparatus for compacting the paving material in road building, which material is applied to a precompacted subgrade by a paving machine.

It is known that paving machines receive the paving material in a hopper from a rear-dumping truck. From the hopper the material is drawn off by a conveying system and metering means to a screw distributor which deposits the material in placement thicknesses of up to 30 cm and more onto a precompacted subgrade. A heated finishing beam then strikes off the material and it is compacted from the surface by means of a tamper and vibration compacting apparatus, both of which are disposed in an adjustable or controllable leveling de-' VlCe.

In addition to achieving a certain degree of finish, the technological purpose of this compacting operation is to ensure that the paving material is deposited in a mat as densely as possible to enable the subsequent roller passes to be minimized. Since modern road building apparatus is capable of reaching operating speeds of up to 50 m/min with a working width of up to 5 m, it is clear that the saving of roller passes by adequate precompaction will be significant.

The known method of compacting the paving material as described hereinabove has a number of defects and disadvantages. The placement material differs widely from case to case in regard to its compacting properties; asphalt concretes, having a high content of chips, may be very friable; bituminous carriageway surfacings comprise very cohesive material; while asphalt pavement of plastic-viscous material and lean concretes are stiffly plastic and of comparatively little cohesion. Accordingly, dynamic processing of the material from its exposed surface is not adequate in all cases. Frequently an impact beam (tamper) merely kneads the material and provides a compacting action only by virtue of the fact that it rams the material under the compacting apparatus which follows. Even a noticeable self-compacting effect covers only the strata near the surface and allows the underside of the strata of paving material to remain as a spongy fill deposit. in the upper range of the paving machine operating speed it is not possible for the impacts to be applied with the sufficient density and uniformity onto the surface of the till, thus resulting in irregularities.

It is known to overcome these difficulties by substantially increasing the impact'frequency of the tamper. However, for technological reasons this requires the use of an electrodynamic drive. On the one hand, this is very complex as regards the driving means and the generation of the operating current and, on the other hand, the high frequencies employed are particularly readily substantially absorbed in cohesive materials so that even in this case the underside of the placed stratum experiences a substantially lesser effect from the action of the compacting apparatus than does the top side.

It is the object of the invention to provide a method for compacting the paving material in road building by means of a paving machine requiring a comparatively smaller technical effort, providing improved compaction of the underside of the stratum of paving material and improving the contact between the underside of the stratum of paving material with the top of the subgrade and thus resulting in better adhesion.

According to the invention, this problem is solved in that the subgrade is excited into oscillations in the feed direction immediately in front of the paving machine so that surface waves of the subgrade cause oscillations from its surface to be introduced into the interface between the subgrade and the paving material. In this respect, the term paving machine is employed herein to identify that device (perhaps part of an overall apparatus) which deposits and at least commences the initial leveling of the paving material onto the subgrade.

To this end the invention utilizes the knowledge that surface waves'have a substantially more favorable conduction mechanism for dynamic conditions than does the propagation of impact processes in the depth of the material. The subgrade is set into oscillations immediately in front of the paving machine and by virtue of the action of the surface waves also below the paving material which is thus quasi-vibrated from below. Accordingly, it is not only the lower strata of the paving material that are being biased in this manner but contact between the paving material and the surface of the subgrade is also improved.

The invention furthermore relates to apparatus for performing the method described hereinabove. Such a method is characterized in its most general form by a vibrator compactor mounted on the road finisher immediately in front of the applied paving material and bearing on the subgrade.

The vibrator compactor may be provided with one or more vibration bands which generate unbalance or it may have one or more vibrator plates which produce unbalance. In an advantageous construction, the working part of the vibrator compactor is loaded through springs by a superimposed load so that the working part operates with the superimposed load. In this case it is possible for the centrifugal force to be higher than the weight. The superimposed load can be produced by hydraulic loading means which bear on the vehicle frame of the paving machine. The orientation of the vibrating force relative to the perpendicular may be adjustable.

In a preferred embodiment, the principal direction in which the vibrating force of the operating part or operating position acts is horizontal relative to the traveling direction of the paving machine. It may then adjust it to a steeper angle relative to this operating direction.

In a further embodiment of the apparatus according to the invention this may be subdivided in a similar manner into individual sets of apparatus. and may thus be constructed so that it can be optionally laterally extended in the same way as corresponding parts of the paving machine, for example, the screw distributor and the smoothing beam.

When using a plurality of individual sets of apparatus, means are preferably provided for producing phase equality between the individual apparatus which functions simultaneously.

Spaces, approximately equivalent to the width of one individual apparatus or the distance between the individual apparatus to the leading edge of the applied material may be provided between the individual sets of apparatus.

The vibrator compactor may be adapted for raising by hydraulic means which also functions as loading apparatus.

THE DRAWING The drawing is a schematic side elevation of an embodiment of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENT The following disclosure is offered for public dissemination in return for the grant of a patent. Although it is detailed to ensure adequacy and aid understanding, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how others may later disguise it by variations in form or additions or further improvements. The claims at the end hereof are intended as the chief aid toward this purpose, as it is these that meet the requirement of pointing out the parts, improvements, or combinations in which the inventive concepts are found.

In the drawing, the numeral refers to a subgrade which is precompacted. Paving material is dumped on the subgrade by a paving machine 12 of known construction. This paving machine has a frame 1 1 on which is mounted a hopper device 13 for a depositing, leveling, smoothing and compacting the paving material into a mat or layer 14. Immediately in front of the material the hopper device 13 and thus thru the applied layer of paving (in traveling direction) the road-finisher 12 has a vibrator compactor with a vibrator plate 16. The vibrator plate 16 is provided with an unbalance vibrator 18. This is guided by a radius rod 20. The right end of the radius rod is pivotally connected to the frame and the left end is pivotally connected to plate 16. Thus the plate is restrained to movement in an are about the right end of the radius rod thrust against the soil by hydraulic cylinders 22 serving as loading means which cylinders bear against the vehicle frame of the paving machine 12. Using a double acting cylinder 22 it also may be employed to raise the plate 16 away from the subgrade.

The subgrade 10 thus has vibrations imposed upon it, the surface waves being propagated over the surface of the subgrade 10 to below the placement material 14 as indicated at 24. Vibrations are therefore induced into the placement material 14 from the surface of the subgrade 10, that is to say from below. These vibrations result in compaction of the lower strata of the placement layer 14 and provide better adhesion of the stratum on the surface of the subgrade.

We claim:

1. In the process of building a road wherein a paving machine moving in a given direction applies a mat of paving material onto a precompacted subgrade, the improvement comprising the step of:

vibrating the subgrade at a location immediately in front, in said direction, of said application to an extent sufficient to impart said vibrations to the subgrade at the interface between the mat and the subgrade and thus to the lower strata of the mat, the vibrations being applied directly to the subgrade and independently of the paving material.

2. In an apparatus for building a road wherein a paving machine moving in a given direction has a frame and a device on said frame for applying a mat of paving material onto a precompacted subgrade, the improvement comprising:

vibrator compactor means mounted on said frame and positioned immediately in front of said device in said direction for vibrating the subgrade at a location immediately in front, in said direction, of said application to an extent sufficient to impart said vibrations to the subgrade at the interface between the mat and the subgrade and thus from the subgrade to the mat, said means having a portion in direct contact with said subgrade at a position in front of, with respect to said direction of movement, said location.

3. In an apparatus according to claim 2, characterized in that the vibrator compactor means is provided with one or more unbalance-energized vibrator plates.

4. In an apparatus according to claim 2, wherein said vibrator compactor means includes a vibrator plate movable with respect to the machine frame, a vibrator connected to said plate, and a radius rod connecting the plate and the machine frame for guiding the movement of the plate.

5. An apparatus as set forth in claim 4, including a mounting connecting the plate and the frame and including hydraulic cylinder means for forcing the plate against the subgrade for loading the vibrator compactor means.

6. In an apparatus as set forth in claim 5, wherein said hydrauliccylinder means is operable for lifting said plate from the subgrade.

* i i t UNITED STATES PATENT OFFICE QERTIFICATE 0F CORRECTION Patent No. 3 752 E92 Dated Auqust 14, 1973 lnventbfls) Alois Paar and Fritz Konig It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 33, "placement" should be-paving-;

Col. 3, line 26, delete "a" before "depositing" Col. 3, lines 28, 29 delete "material" Col, 3, line 30, after "paving" insert -material--;

Col. 3, line 37, "radius rod thrust against" should be -radius rod. The plate is thrust agai'nst--.

Signed and sealed this 18th day of December 1973.

(SEAL) Attest:

EDWARD M. FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents 

1. In the process of building a road wherein a paving machine moving in a given direction applies a mat of paving material onto a precompacted subgrade, the improvement comprising the step of: vibrating the subgrade at a location immediately in front, in said direction, of said application to an extent sufficient to impart said vibrations to the subgrade at the interface between the mat and the subgrade and thus to the lower strata of the mat, the vibrations being applied directly to the subgrade and independently of the paving material.
 2. In an apparatus for building a road wherein a paving machine moving in a given direction has a frame and a device on said frame for applying a mat of paving material onto a precompacted subgrade, the improvement comprising: vibrator compactor means mounted on said frame and positioned immediately in front of said device in said direction for vibrating the subgrade at a location immediately in front, in said direction, of said application to an extent sufficient to impart said vibrations to the subgrade at the interface between the mat and the subgrade and thus from the subgrade to the mat, said means having a portion in direct contact with said subgrade at a position in front of, with respect to said direction of movement, said location.
 3. In an apparatus according to claim 2, characterized in that the vibrator compactor means is provided with one or more unbalance-energized vibrator plates.
 4. In an apparatus according to claim 2, wherein said vibrator compactor means includes a vibrator plate movable with respect to the machine frame, a vibrator connected to said plate, and a radius rod connecting the plate and the machine frame for guiding the movement of the plate.
 5. An apparatus as set forth in claim 4, including a mounting connecting the plate and the frame and including hydrAulic cylinder means for forcing the plate against the subgrade for loading the vibrator compactor means.
 6. In an apparatus as set forth in claim 5, wherein said hydraulic cylinder means is operable for lifting said plate from the subgrade. 